Industrial water is often heated to a level sufficient to cause thermal pollution if returned to the environment. There is a growing concern over ecological damage caused by introduction of industrially heated waters to lakes and streams. Not only does such thermal pollution seriously flaw the body of water as a source of an industrial coolant, but may adversely affect the plant and animal life supported thereby.
Large quantities of water may be used by industry without serious depletion or pollution of the available supply by circulating the heated water through a cooling tower, wherein the water is cooled by transfer of heat to air, with which it is intimately mixed and by heat of vaporization to a small percentage of the water which evaporates. However, this method, which represents the current practice and state of the art, requires the erection of large and elaborate structures with expensive and energy-consuming equipment.
In accordance with present practice, high pressure pumps are required to carry the hot water to the tops of tall structures where it is released to fall through layers of fill material. Since the only function of such high pressure pumps is to deliver the water to the cooling process, without actually playing any part therein, the energy required to operate them is largely wasted.
In addition, mechanical draft cooling towers presently require the employment of very large motors, gear reduction units, and propellers as a means of moving the cooling air through these towers. This equipment represents a major portion of the initial cost of each cooling tower installation, in part because of the cost of the components themselves, and in part due to the location of this heavy equipment at the top of the tower, which necessitates extremely heavy and complex structures to support the static dynamic loads imposed.
Of even greater importance is the continuing cost of operation and the consumption of energy involved in the operation of these motors and fans as the principal means of creating draft, i.e., moving cooling air through the tower. Over the life span of such mechanical draft cooling towers, operating costs represent many times the cost of installation.